pop3 and smtp connection timeout from client to server

We have a customer that having a single firewall (202.73.42.163) and around 50 clients pc using pop3 to retrieve email. However, the connection to the server is intermittent, meaning for those 50 users, some of them having a problem of connection time out when their pc initiated the pop3 and smtp connection to the server. Below is the firewall log file for the issue.

We have a customer that having a single firewall (202.73.42.163) and around 50 clients pc using pop3 to retrieve email. However, the connection to the server is intermittent, meaning for those 50 users, some of them having a problem of connection time out when their pc initiated the pop3 and smtp connection to the server. Below is the firewall log file for the issue.